Hand wrenches: features and varieties

The wrench is one of the most important devices that man invented to combat the shortcomings of his other invention - the threaded connection. It is widely used in both industrial and household purposes, making it several times easier to tighten and unscrew a stuck or rusted nut, or other threaded connection. With its help, it is easy to disassemble any large-sized metal structure, even if it has been under the influence of atmospheric influences for a long time.

Hand-operated nutrunners can be characterized as highly specialized devices designed for mounting and dismounting threaded connections. Simply put, these are improved wrenches that use the principle of increasing torque power. The wrench is quite compact, but it has a lot of power and can handle the largest hardware sizes. Due to its original appearance, this tool is somewhat similar to a meat grinder. For this reason, the drivers called him that.

The design of mechanical wrenches includes a lever, a planetary gearbox (also called a multiplier), an emphasis and a cartridge into which nozzles are inserted. The planetary gearbox increases the force applied to the rotation of the handle by more than 70–80 times. Such power loads required the use of durable materials, therefore, alloy steel is used for the manufacture of all parts of the wrench mechanism.

It is worth considering the following features of the impact wrench:

• the tool has the opposite direction of rotation, that is, when the handle is turned in a clockwise direction, the nut will turn clockwise and vice versa;
• you need to set the stop correctly, because, for example, when loosening / tightening the wheel nuts on the left and right side of the car, its location will change;
• when tightening a nut or bolt with such a tool, special care is needed; since there is a manifold increase in power, threads are often folded and bolts are broken.

Most often, manual torque wrenches with a gearbox are used in industrial production for the installation and dismantling of fasteners for large metal structures. He found his other purpose in a car repair shop, where he became very much in demand. It is also often used on construction sites, in shipbuilding and other areas of production. Its widespread use by locksmiths is due to the need to work with massive structures or loaded threaded connections, which are problematic to disassemble with a conventional tool.

At home, these tools cannot be attributed to the necessary tools, which, for example, are screwdrivers, since they are easily replaced by wrenches or wheel wrenches, and a large tightening power is not required. As a rule, truckers buy such a device - it is very convenient for them to change broken wheels on trips without wasting much time. The "meat grinder" will also come in handy in the implementation of some home construction project, where large threaded connections are used.

According to the principle of operation, a manual wrench can be of several types.

• Pneumatic. Such wrenches are the most compact in size, have a higher speed and accuracy. They found the widest application in car repair shops and service stations.
• Hydraulic. Hydraulically driven impact wrenches have the highest efficiency. When using them, there is practically no vibration during operation, their resource is higher than other types, they are very wear-resistant. Manual hydraulic impact wrenches are rare and only in production, since they are mainly stationary equipment and are too large for manual use. These are professional tools.
• Electric. This wrench is a high-speed, high-precision tool with almost no vibration. In turn, they are subdivided into wrenches operating from the mains and from batteries. This type of equipment is effective, but manual models do not have enough power, for example, to quickly change a truck wheel on the road.
• Mechanical. Considering all the advantages of other types, the impact wrench, based on the mechanical principle of action, has become the most popular. The advantages of the mechanical principle of operation are great smoothness of loosening, uniformity of force, and a low percentage of broken bolts.

In addition, pneumatic and electric impact wrenches are available. This means that they implement the principle of operation, in which special hammers are included in the tool mechanism, which increase the torque, which does not lead to increased vibration of the tool body itself. As a rule, with such impact wrenches (including those with elongated, that is, using an elongated shaft), special type heads are used - impact heads. They differ because they relate to the material from which the impact heads are made (in both cases, the same CR-V chromium vanadium alloy is used). The use of a thin-walled impact head is often found (they work with it when installing disks on tire changers), and thick-walled heads are called power heads.

It is worth considering in more detail the main characteristics of a hand wrench.

• Gear ratios. The most common gear ratio of such a "meat grinder" is a ratio of 1: 56, that is, when the handle makes 56 full turns, the tool head can make only one revolution. This slow rotation is not used to completely loosen the nut. The "meat grinder" is used at the first stage to remove the stuck fasteners, and later on it is much faster to use a regular key or unscrew it by hand. A nutrunner has also been implemented that operates according to a two-speed scheme, which allows changing the gear ratio according to the formula 1: 3. In this version, the nut can be completely unscrewed with a nutrunner. It is not necessary to resort to using a wrench, as the unscrewing time when switching to second speed is reduced.
• Torque / Torque. It determines the force that will be applied by the wrench to the nut. It is measured in newton meters (Nm). Different types of work require the application of the appropriate amount of torque. If it is necessary to unscrew the car wheel bolts, an effort of only a couple of hundred Nm is required. It would never occur to anyone to use a heavy, powerful wrench that develops force five times more.

• A square for a nozzle. The technical specification defines the use of a square wrench-socket connection. Its size determines the size of the connections that this tool works with.For example, a 10-16mm fastener will require a half-inch square, and a 20-50mm nut will require a square of at least one inch.
• Wrench size. Of course, the dimensions of the wrench affect the ease of use and transportation. Typically, more powerful tools are larger.

The advantages of a manual mechanical wrench are as follows:

• the use of a multiplier that converts torque and enhances it;
• simple design and, as a result, reliability;
• smooth unscrewing of a threaded connection;
• lack of dependence on the availability of the power grid;
• small size.

A relatively large mass of the tool can be considered a disadvantage, but it should be borne in mind that it is caused by the use of reliable and durable metals and alloys in the design. Today, the combination "strong but light" implies too high a cost for such a wrench. They also sometimes blame him for a relatively high power, since it is easy to break a hairpin or break a thread. But this is not true, since any, even the simplest tool, requires careful and careful handling.

The use of any mechanical device requires compliance with certain requirements. For example, the body and elements of the planetary gearbox (handle, heads) should not have burrs and irregularities, the heads and handles should not allow backlash, and should be put on the spindle normally. The use of worn heads with broken hexagons is prohibited. For a power tool, it is additionally necessary to periodically check the integrity of the cable, isolate the wiping places.

From the video below, you can learn how to unscrew the wheels with a hand wrench.